Unit 2 Lesson 3 — Fiber Optic Cabling & Connections

Networking • Class Notes

Guiding Question

How do the different types of fiber optic cables, connectors, and transceivers impact network performance, and how do they support various communication needs?

Lesson Objectives

Compare single-mode and multimode fiber (speed, distance, use cases).
Identify common fiber optic connectors and describe their applications.
Explain how transceivers connect devices to fiber networks.
Differentiate transceivers by protocol and form factor (SFP vs. QSFP).
Evaluate how fiber components affect network design, performance, and scalability.

1) Fiber Optic Media

Data travels as light impulses generated by an LED (multimode) or a laser (single-mode).

Safety Warning: Single-mode lasers operate at wavelengths invisible to the eye and can cause serious eye damage. Never look into an active fiber.

2) How Fiber Works

Prevent refraction into the cladding.
Maintain internal reflection within the core.

When both are met, the light bounces down the core to the receiver accurately.

3) Key Media Selection Questions

Cabling Type
What carries the data signal?

Speed
How much data per second?

Connector
Which connector fits the media/device?

Standards
Which IEEE/industry spec applies?

Distance
How far before signal loss?

4) Single-Mode Fiber (SMF)

Core Diameter: ~8–10 μm
Light Source: Laser
Transmission: Single, near-straight optical path → highest bandwidth & longest distance
Speed & Standards: 1 Gbps = 1000Base-LX; 10 Gbps = 10GBase-LX
Distance: Up to ~100 km (may require amplification)
Use Cases: Long-haul telecom, high-speed inter-DC links

5) Multimode Fiber (MMF)

Core Diameter: ~50 or 62.5 μm
Light Source: LED
Transmission: Multiple paths (modes) within the core
Speed & Standards: 1 Gbps = 1000Base-SX; 10 Gbps = 10GBase-SX
Distance: High speeds to ~500 m; lower speeds to ~2 km
Use Cases: Intra-building runs, data halls, campus backbone segments

6) Fiber Optic Connectors

Connector	Description	Common Use
SC (Subscriber Connector)	Push-pull, square body	Enterprise & carrier equipment
LC (Local Connector)	Small form-factor, latch	High-density switch/optics panels
ST (Straight Tip)	Bayonet, spring-loaded	Legacy networks, labs
MPO (Multi-Fiber Push-On)	Arrays of 12/24/48 fibers	Data centers, trunk cables

7) Advantages & Disadvantages

Advantages

Immune to electromagnetic interference (EMI)
Low signal loss over long distances
Very lightweight (≈9 lbs per 1000 ft vs. ≈80 lbs for coax)
Safety: Non-conductive (no spark/fire risk)
Security: Difficult to tap; minimal radiation

Disadvantages

Higher material and optics/transceiver cost
Specialized installation and termination
Susceptible to modal/physical disturbances (temperature, pressure, vibration)

8) Transceivers

Transceivers convert electrical Ethernet signals (copper) to optical signals (fiber) and back, allowing mixed-media networks.

Example: A fiber patch leads into a pluggable transceiver, which inserts into a switch port for seamless integration.

9) Transceiver Form Factors

Form Factor	Channels	Typical Rates	Notes
SFP	1	≈ 5 Gbps	Compact single-channel optic
SFP+	1	≈ 16 Gbps	Higher-speed SFP evolution
SFP28	1	≈ 28 Gbps	25–28 G class optics
QSFP	4	≈ 4 × 1.25 = 6 Gbps	Quad-lane aggregation
QSFP+	4	≈ 4 × 10 = 40 Gbps	40G data center staple
QSFP28	4	≈ 4 × 28 = 112 Gbps	100G/112G class deployments

Summary

Fiber optics deliver ultra-fast, long-distance, and secure networking using light. Knowing when to choose SMF vs. MMF, which connector to deploy, and the right transceiver form factor is essential for designing scalable, high-performance networks.